marked some CRITICAL sections;
eliminated transform_failure (to avoid critical section for main transactions);
removed unused exceptions MetaSimplifier.SIMPROC_FAIL, Attrib.ATTRIB_FAIL, Method.METHOD_FAIL, Antiquote.ANTIQUOTE_FAIL;
use "../settings.ML";
use_thy "Tree";
use_thy "Tree2";
use_thy "Plus";
use_thy "case_exprs";
use_thy "fakenat";
use_thy "natsum";
use_thy "pairs";
use_thy "Option2";
use_thy "types";
use_thy "prime_def";
use_thy "simp";
use_thy "Itrev";
use_thy "AdvancedInd";
use_thy "appendix";